A Personal Area Network (PAN) includes multiple devices such as a computer, phone, Personal Digital Assistant (PDA), headset or earpiece, imager or camera, a body-worn sensor such as a for measuring exercise such as gait, respiration or heart function, or other health related sensors such as blood pressure, blood chemistry, etc, a keyboard, mouse, printer, and so forth. Each of these devices is capable of functioning separately, and may therefore require a separate energy source. A user maintains these energy sources. Typically, these devices are portable and the user has to carry them from place to place. Consequently, the user also has to carry the separate energy source for each device.
Ideally each device is designed so that the energy storage capacity is sufficient for a time of usage which is the same for all of the devices. While the amount of fuel needed is predictable for normal use cases, there are exceptional use cases where certain devices require more energy than normal. There are inevitably situations in which energy replenishment is needed for only one device while the other devices have plenty of available energy, which may be inconvenient or distracting to the user.
Over the last few years, the use of fuel cells as an energy source has increased. Fuel cells work on the principle of converting chemical energy into electrical energy. This principle is also known as electro-chemical conversion of energy. The fuels required for fuel cells may be in gas form, such as hydrogen and oxygen, or they may be in liquid form, such as methanol, or specialized alcohols.
Each fuel cell contains a fuel container as to carry the fuel which requires refilling from a separate fuel storage container, which is inconvenient since it requires the user to manually attach the devices to the separate fuel container whenever the devices run out of fuel. To overcome this problem, conventional solutions include the use of a battery powered PAN devices with a common fuel cell. According to this solution, a common fuel cell provides an electronic connection for charging each of the batteries in the devices. Since the fuel cell supplies energy via charging to the batteries, an electro-chemical conversion first takes place in the fuel cell, and then another electro-chemical conversion takes place in the battery. However, the two electro-chemical conversions in series result in a loss of energy. The reverse transfer of energy from a battery back to a fuel cell is also inefficient and furthermore requires special equipment which may be unduly expensive for the purpose of redistributing energy among personal area network devices.
Accordingly, there is a need for a convenient and more efficient method of supplying or redistributing energy among the devices in a personal area network, by a mechanism that requires only one electrochemical conversion of energy.